Hi Marathon Man,
Obviously, the lifecycling-repurposing-recycling options are preferable, but the following (from Wikipedia) suggests that disposing of polystyrene through incineration and/or land-fill is not as bad as one might suspect:
"Foam cups and other polystyrene products can be safely buried in landfills, since it is
as stable as concrete or brick. No plastic film is required to protect the air and underground water.
"Paper cups, when incinerated, produce an average of 200 pounds of ash per ton. If polystyrene is
properly incinerated at high temperatures, one ton of foam cups produces 0.2 ounces of ash. The only chemicals generated are water, carbon dioxide, some volatile compounds, and carbon soot."
Details here:
http://en.wikipedia.org/wiki/Polystyrene
As stable as concrete or brick? It seems that this stuff is made to last -- it really doesn't (bio?)degrade. Next time you are on a beach, check out the amount of polystrene and other plastics in the shingle/sand...
Regards
Chris P
Admin